1. Field of the Invention
The present invention generally relates to a Nd—Fe—B magnet and a method of preparing a hard aluminum film on the surface of the Nd—Fe—B magnet.
2. Description of the Prior Art
Due to the potential difference between the Nd-rich phase and the Nd2Fe14B phase, and the hydrogen absorption properties of an Nd—Fe—B magnet, it is very easy for the Nd—Fe—B magnet to corrode. To prevent the Nd—Fe—B magnet from corroding, it is known in the art to provide an anti-corrosive coating layer on the surface of the Nd—Fe—B magnet. The known methods include:                a. Electroplating—a widely used method for the preparation of an anti-corrosion coating on the surface of the Nd—Fe—B magnet. However, the use of the electroplating method is becoming more and more restrictive because the electroplating method damages the Nd—Fe—B magnet and the environment.        b. Arc ion plating, magnetron sputtering, magnetic control arc ion plating, and vacuum evaporation methods are generally used to form a first film of aluminum on the surface of the Nd—Fe—B magnet. However, the first film of aluminum on the surface of the Nd—Fe—B magnets is soft which can be easily damaged thereby affecting the anti-corrosion effect of the first film of aluminum.        